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BACKGROUND: The sustainable elimination of Triatoma infestans in the Gran Chaco region represents an enduring challenge. Following the limited effects of a routine pyrethroid insecticide spraying campaign conducted over 2011-2013 (first period) in Avia Terai, an endemic municipality with approximately 2300 houses, we implemented a rapid-impact intervention package to suppress house infestation across the urban-to-rural gradient over 2015-2019 (second period). Here, we assess their impacts and whether persisting infestations were associated with pyrethroid resistance. METHODS: The 2011-2013 campaign achieved a limited detection and spray coverage across settings (< 68%), more so during the surveillance phase. Following community mobilization and school-based interventions, the 2015-2019 program assessed baseline house infestation using a stratified sampling strategy; sprayed all rural houses with suspension concentrate beta-cypermethrin, and selectively sprayed infested and adjacent houses in urban and peri-urban settings; and monitored house infestation and performed selective treatments over the follow-up. RESULTS: Over the first period, house infestation returned to pre-intervention levels within 3-4 years. The adjusted relative odds of house infestation between 2011-2013 and 2015-2016 differed very little (adj. OR: 1.17, 95% CI 0.91-1.51). Over the second period, infestation decreased significantly between 0 and 1 year post-spraying (YPS) (adj. OR: 0.36, 95% CI 0.28-0.46), with heterogeneous effects across the gradient. Mean bug abundance also dropped between 0 and 1 YPS and thereafter remained stable in rural and peri-urban areas. Using multiple regression models, house infestation and bug abundance at 1 YPS were 3-4 times higher if the house had been infested before treatment, or was scored as high-risk or non-participating. No low-risk house was ever infested. Persistent foci over two successive surveys increased from 30.0 to 59.3% across the gradient. Infestation was more concentrated in peridomestic rather than domestic habitats. Discriminating-dose bioassays showed incipient or moderate pyrethroid resistance in 7% of 28 triatomine populations collected over 2015-2016 and in 83% of 52 post-spraying populations. CONCLUSIONS: The intervention package was substantially more effective than the routine insecticide spraying campaign, though the effects were lower than predicted due to unexpected incipient or moderate pyrethroid resistance. Increased awareness and diagnosis of vector control failures in the Gran Chaco, including appropriate remedial actions, are greatly needed.

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BACKGROUND: Chemical control with pyrethroid insecticides has been effective in reducing endemic areas of distribution of Triatoma infestans in the Southern Cone, as well as Bolivia; this had considerably reduced the infestation of households in a large part of the territory. Nowadays, areas such as the Chaco and the Inter-Andean Valleys are regions where the reach of vector control strategies is becoming limited, and infestations of insecticide-treated households are reported more often. The objective of this study was to determine if the persistence of T. infestans stems from changes in the susceptibility of its toxicological profile in four communities in the municipality of Toro Toro, Potosi, Bolivia. METHODS: Susceptibility to deltamethrin of wild and domestic populations of T. infestans was evaluated in two stages (16 populations before and 13 populations after spraying) among DUs (structures in the intra- and peridomicile) and wild ecotopes, in four communities. Serial dilutions of deltamethrin in acetone (0.2 µl) were applied topically on standardized first-stage nymphs. Dose-response results were analyzed with the software PoloPlus and the relationships between lethal doses (LD) and resistance ratios (RR50) were determined. RESULTS: Different degrees of RR50 were detected among the populations before and after spraying (25.66-54.70 and 21.91-40.67, respectively), as well as in different ecotopes within a DU (DU JC 3, 28.06-36.13, in mixed structures of corrals and chicken coops; and DU JG 3, 46.27-25.70, in kitchen roofs), or in the wild environment of the community JG Sil (29.21-40.67). The mortality of insects undergoing diagnostic dose (DD) was never higher than 34%. CONCLUSION: The results obtained in this study showed resistance of T. infestans to deltamethrin in four communities, hence the complexity of this phenomenon is not only limited to the level of communities, but also applies to the microgeographical level, as in different ecotopes present within the DUs. This phenomenon should be considered while planning the activities of control programs.

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Insecticide resistance is a broadly recognized ecological backlash resulting from insecticide use and is widely reported among arthropod pest species with well-recognized underlying mechanisms and consequences. Nonetheless, insecticide resistance is the subject of evolving conceptual views that introduces a different concept useful if recognized in its own right - the risk or likelihood of control failure. Here we suggest an experimental approach to assess the likelihood of control failure of an insecticide allowing for consistent decision-making regarding management of insecticide resistance. We also challenge the current emphasis on limited spatial sampling of arthropod populations for resistance diagnosis in favor of comprehensive spatial sampling. This necessarily requires larger population sampling - aiming to use spatial analysis in area-wide surveys - to recognize focal points of insecticide resistance and/or control failure that will better direct management efforts. The continuous geographical scale of such surveys will depend on the arthropod pest species, the pattern of insecticide use and many other potential factors. Regardless, distance dependence among sampling sites should still hold, following the maxim that the closer two things are, the more they resemble each other, which is the basis of Tobler's First Law of Geography. © 2016 Society of Chemical Industry.

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INTRODUCTION:: The Housing Improvement Program for Chagas Disease Control (HIPCDC) was established in 2001 in Northwestern Rio Grande do Sul State, aiming to improve the conditions of the domiciliary and peridomiciliary environments to make them resistant to triatomine colonization. This study aimed to assess the impact of the HIPCDC on triatomine control by developing local population and authority awareness on the issue. METHODS:: The study was conducted by means of questionnaires applied to local authorities and the program beneficiaries. Three municipalities - Ajuricaba, Coronel Barros, and Crissiumal - were visited. RESULTS:: A program coordinator from each municipality and 62 individuals from selected households were interviewed. The authorities reported difficulties in the implementation of the program due to differences between the project development period and financial resource availability, in addition to a lack of understanding by the community not included in the program. As for the houses, most improvements were made in the peridomiciliary environments; moreover, construction of 4 new residences, as well as the renovation of others, was also reported. Regarding suggestions to the program, requests for better planning (44.9%) and renovation quality (36.7%) were highlighted. With reference to the presence of triatomine bugs, prior to the HIPCDC adaptations, 12.9% of the respondents reported coming across at least one specimen at home, as compared to 22.6% who found these insects in peridomiciliary areas. CONCLUSIONS:: Despite reports of difficulties in carrying out the HIPCDC, there was an improvement in the housing conditions, with no triatomine occurrence reports after the program implementation.

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Abstract INTRODUCTION: The Housing Improvement Program for Chagas Disease Control (HIPCDC) was established in 2001 in Northwestern Rio Grande do Sul State, aiming to improve the conditions of the domiciliary and peridomiciliary environments to make them resistant to triatomine colonization. This study aimed to assess the impact of the HIPCDC on triatomine control by developing local population and authority awareness on the issue. METHODS: The study was conducted by means of questionnaires applied to local authorities and the program beneficiaries. Three municipalities - Ajuricaba, Coronel Barros, and Crissiumal - were visited. RESULTS: A program coordinator from each municipality and 62 individuals from selected households were interviewed. The authorities reported difficulties in the implementation of the program due to differences between the project development period and financial resource availability, in addition to a lack of understanding by the community not included in the program. As for the houses, most improvements were made in the peridomiciliary environments; moreover, construction of 4 new residences, as well as the renovation of others, was also reported. Regarding suggestions to the program, requests for better planning (44.9%) and renovation quality (36.7%) were highlighted. With reference to the presence of triatomine bugs, prior to the HIPCDC adaptations, 12.9% of the respondents reported coming across at least one specimen at home, as compared to 22.6% who found these insects in peridomiciliary areas. CONCLUSIONS: Despite reports of difficulties in carrying out the HIPCDC, there was an improvement in the housing conditions, with no triatomine occurrence reports after the program implementation.

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Phlebotominae are the vectors of Leishmania parasites. It is important to have available surveillance and collection methods for the sand fly vectors. The objectives of the present study were to evaluate and compare traps for the collection of sand fly species and to analyze trap catches along months and transects. Field evaluations over a year were conducted in an endemic area of leishmaniasis in the state of Quintana Roo, Mexico. A randomized-block design was implemented in study area with tropical rainforest vegetation. The study design utilized 4 transects with 11 trap types: 1) Centers for Disease Control and Prevention (CDC) light trap with incandescent bulb (CDC-I), 2) CDC light trap with blue light-emitting diodes (LEDs) (CDC-B), 3) CDC light trap with white LEDs (CDC-W), 4) CDC light trap with red LEDs (CDC-R), 5) CDC light trap with green LEDs (CDC-G), 6) Disney trap, 7) Disney trap with white LEDs, 8) sticky panels, 9) sticky panels with white LEDs, 10) delta-like trap, and 11) delta-like trap with white LEDs. A total of 1,014 specimens of 13 species and 2 genera (Lutzomyia and Brumptomyia) were collected. There were significant differences in the mean number of sand flies caught with the 11 traps; CDC-I was (P  =  0.0000) more effective than the other traps. Other traps exhibited the following results: CDC-W (17.46%), CDC-B (15.68%), CDC-G (14.89%), and CDC-R (14.30%). The relative abundance of different species varied according to trap types used, and the CDC-I trap attracted more specimens of the known vectors of Leishmania spp., such as like Lutzomyia cruciata, Lu. shannoni, and Lu. ovallesi. Disney trap captured more specimens of Lu. olmeca olmeca. Based on abundance and number of species, CDC light traps and Disney traps appeared to be good candidates for use in vector surveillance programs in this endemic area of Mexico.

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In a recent article in the Reader's Opinion, advantages and disadvantages of the certification processes of interrupted Chagas disease transmission (American trypanosomiasis) by native vector were discussed. Such concept, accepted by those authors for the case of endemic situations with introduced vectors, has been built on a long and laborious process by endemic countries and Subregional Initiatives for Prevention, Control and Treatment of Chagas, with Technical Secretariat of the Pan American Health Organization/World Health Organization, to create a horizon target and goal to concentrate priorities and resource allocation and actions. With varying degrees of sucess, which are not replaceable for a certificate of good practice, has allowed during 23 years to safeguard the effective control of transmission of Trypanosoma cruzi not to hundreds of thousands, but millions of people at risk conditions, truly "the art of the possible."

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Certifying the absence of Chagas disease transmission by native vectors lacks scientific grounds and weakens long-term control-surveillance systems to the detriment of people living under risk conditions. Instead, a regular "certification of good practice" (including vector control-surveillance, case detection/patient care and blood safety) could help achieve sustained disease control.

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Certifying the absence of Chagas disease transmission by native vectors lacks scientific grounds and weakens long-term control-surveillance systems to the detriment of people living under risk conditions. Instead, a regular "certification of good practice" (including vector control-surveillance, case detection/patient care and blood safety) could help achieve sustained disease control.

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Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite, Trypanosoma cruzi. The main mode of transmission of this disease in endemic areas is through an insect vector called triatomine bug. Triatomines become infected with T. cruzi by feeding blood of an infected person or animal. Chagas disease is considered the most important vector borne infection in Latin America. It is estimated that between 16 and 18 millions of persons are infected with T. cruzi, and at least 20,000 deaths each year. In this work we formulate a model for the transmission of this infection among humans, vectors and domestic mammals. Our main objective is to assess the effectiveness of Chagas disease control measures. For this, we do sensitivity analysis of the basic reproductive number R0 and the endemic proportions with respect to epidemiological and demographic parameters.

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Although fruit fly host status determination/designation lies at the heart of strategic decisions on national and international trade of fruit and vegetables, all attempts thus far to define host plant status have been contentious and as a result long-standing disputes between commercial partners throughout the world have lingered over decades. Part of the problem is that too little effort has been devoted to understanding the underlying mechanisms involved in host plant use by fruit flies and that instead economic and political interests usually prevail. Here we review the most important evolutionary, biological, ecological, physiological, and behavioral aspects that drive host use by fruit flies, and then construct a flow diagram rooted in these fundamentals that outlines a series of steps and definitions to determine if a particular fruit or vegetable (and cultivars thereof) is a natural host, or a conditional (potential, artificial) host, or a nonhost. Along the way, we incorporate risk analysis considerations and propose that the underlying complexity determining host plant utilization by fruit flies requires a flexible systems approach capable of realistically dealing with fly/host/environment/geographic variability on a case-by-case basis.

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The repeated use of permethrin and other insecticides for the control of head lice, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), during past decades has resulted in the development of marked levels of resistance. Thus, new alternative insecticides are needed for the control of head lice. We studied the fumigant and repellent properties of essential oils from 16 native and exotic plants in Argentina, and 21 chemical components against permethrin-resistant head lice from Argentina. With a direct vapor-exposure bioassay, the most effective oil was from the native Myrcianthes cisplatensis Cambess (Myrtaceae) with a time to 50% knockdown (KT50) of 1.3 min, followed by exotic species, Eucalyptus cinerea F.V. Muell., Eucalyptus viminalis Labill., and Eucalyptus saligna Smith. with KT50 values of 12.0, 14.9, and 17.4 min, respectively. The most effective components were 1,8-cineole and anisole, with KT50 values of 11.1 and 12.7 min, respectively. Regression analysis of KT50 values and vapor pressures and water-partition coefficients for the essential oil components revealed that the most effective fumigants were among the more volatile components. Repellency assays indicated that the essential oil from Mentha pulegium L. and its benzyl alcohol component were the most effective repellents, having repellency indices of 75.5 and 57.8%, respectively. Thus, some Argentinean plants contain essential oils and components that function as fumigants or as repellents and thereby show potential for development of new control products for head lice.

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The impact of control activities against Triatoma infestans (Klug) (Hemiptera: Reduviidae) in South America has a marked contrast within and outside the Gran Chaco region. Development of a geographic information system, as part of an improvement in control program activities, allowed analysis of the spatial pattern of house infestations by T. infestans before and after house spraying with deltamethrin in the San Martin Department (an arid Chaco region of central Argentina). The overall peridomestic infestation index decreased from 48.2 to 28.2% after insecticide application. House infestation was spatially clustered in regions with low or high infestation levels that were located east and southwest of the department, respectively. This pattern was detected both before and after the insecticide application. Three environmental variables calculated from a temporal series of MODIS imagery (average of night temperature, maximum of day temperature, and temporal variation of vegetation index) were capable of correctly discriminating 96% of the places belonging to either high or low house infestation observed after the insecticide application.

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The first three months of 2002 witnessed a dengue epidemic in the State of Rio de Janeiro. At that time, health authorities encouraged community participation in the elimination of vector breeding sites. For this campaign, a great quantity of information about the disease was extensively publicized in order to guide the population's preventive action. This paper analyzed the three pamphlets most widely distributed at that time in Rio de Janeiro city considering that this information contributed to the construction of disease representation and its prevention. It was observed that even though this information was provided repeatedly it must be revised.

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Most Latin American countries are making dramatic progress in controlling Chagas disease, through a series of national and international initiatives focusing on elimination of domestic populations of Triatominae, improved screening of blood donors, and clinical support and treatment of persons infected with Trypanosoma cruzi. Some countries, particularly Uruguay, Chile and Brazil, are sufficiently advanced in their programmes to initiate detailed planning of the subsequent phases of Chagas disease control, while others such as Peru, Ecuador, and Mexico, are currently applying only the initial phases of the control campaigns. In this review, we seek to provide a brief history of the campaigns as a basis for discussion of future interventions. Our aim is to relate operational needs to the underlying biological aspects that have made Chagas disease so serious in Latin America but have also revealed the epidemiological vulnerability of this disease. The English version of this paper is available too at: http://www.insp.mx/salud/index.html.

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Most Latin American countries are making dramatic progress in controlling Chagas disease, through a series of national and international initiatives focusing on elimination of domestic populations of Triatominae, improved screening of blood donors, and clinical support and treatment of persons infected with Trypanosoma cruzi. Some countries, particularly Uruguay, Chile and Brazil, are sufficiently advanced in their programmes to initiate detailed planning of the subsequent phases of Chagas disease control, while others such as Peru, Ecuador, and Mexico, are currently applying only the initial phases of the control campaigns. In this review, we seek to provide a brief history of the campaigns as a basis for discussion of future interventions. Our aim is to relate operational needs to the underlying biological aspects that have made Chagas disease so serious in Latin America but have also revealed the epidemiological vulnerability of this disease

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A vigilância entomológica da doença de Chagas no Estado de Säo Paulo tem adotado um esquema que considera a localidade como unidade de trabalho e prioriza as açöes de acordo com níveis de infestaçäo obtidos a partir de buscas sistemáticas de triatomíneos (rotina) na área mais infestada e nas residências de moradores que notificam presença desses insetos (atendimento a notificaçäo). As espécies triatomínicas de maior presença no Estado atualmente säo Triatoma sordida e Panstrongylus megistus. Um estudo comparativo dos índices de infestaçäo obtidos para casas e peridomicílios em pesquisas de rotina e atendimento à notificaçäo nos biênios 90/91, 92/93 e 94/95, apontou percentuais médios de positividade para intradomicílio de 1,3 na rotina e 6,2 no atendimento. Para o peridomicílio os valores foram de 8,6 e l8,2, respectivamente, sem diferença entre os biênios. Os atendimentos às notificaçöes demonstraram percentuais médios de positividade (encontro de foco) em 26 por cento das casas. Foi constatado ainda que as noticicaçöes procederam de localidades com níveis de infestaçäo iniciais nulos (I = 0), intermediários (I < 5) e elevados (I > 5), näo obstante os percentuais de atendimentos positivos terem sido maiores naquelas cujos níveis de infestaçäo iniciais eram elevados. Estes dados reforçam a importância da notificaçäo na vigilância de espécies vetoras que se caracterizam pelo caráter invasivo, como aquelas presentes atualmente no Estado de Säo Paulo

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Approximately 2 million people in Argentina are infected with Trypanosoma cruzi, the etiologic agent of Chagas disease, thereby constituting the major tropical disease in the country. As in other six Southern Cone countries, Triatoma infestans is the only or major vector of T. cruzi among human and domestic animals. In Argentina, a vertically structured National Chagas Control Program was established in 1962. Such a program pursued the elimination of domestic and peri-domestic populations of T. infestans through insecticidal spraying, and the serological control of blood donors to prevent transfusion-related infections. This program strongly reduced the nation-wide serological prevalence of T. cruzi in the population. For example, in 18 or 20 year-old men drafted into military service, the seroprevalence decreased from 10.1% in 1964 for those who had been born in 1944 to 1.9% in 1993 for those born in 1975. However, the vertical strategy failed to reach and sustain the surveillance phase in widespread rural areas with disperse populations due to its intrinsic limitations and the reduced priority level assigned to rural health programs. An alternative, horizontally-structured control strategy of T. infestans was developed and assayed in the Province of Santiago del Estero between 1985-1989, and 1991-1992. The projects demonstrated that insecticidal spraying carried out with community participation combined effectiveness and commitment in such a way as to produce a strong impact on house reinfestation and the extension of the area under entomological surveillance. This experience has been transferred in a chain of responsibilities to the personnel of the National Chagas Control Program, using participating workshops, procedural guidelines, and practical training. This personnel transferred the strategy using similar methods to the field health care agents and volunteers chosen by their own communities (community leaders). After the workshops, the leaders received all the materials needed to install and develop the ongoing surveillance activities: third generation pyrethroid insecticides, manuals, hand-operated sprayers, and sensor boxes to detect domiciliary infestations. From 1993 to 1998, a total of 15,000 health care agents or community leaders were trained. A total of 675,000 houses were sprayed with residual insecticides in the attack phase, and 850,000 houses entered the surveillance phase. This is the first time that such large coverage has been accomplished in Argentina. The network of laboratories installed a quality assurance program to current serological procedures applied to blood donors, organ transplant, and the detection and treatment of newborns to women sero-reactive for T. cruzi in Argentina. We expect to interrupt the vector-mediated transmission of T. cruzi in the next 18 months, but the sustainability of such a program depends on, at least, additional work with the community to achieve a change of attitudes and practices related to house infestation for the next 10 years. A social effort will be needed to cover those expenses, but the expected economic returns exceed largely the cost of any such program, as suggested by cost-benefit studies. To illustrate, the annual treatment costs of one Chagas patient can help maintain 25 households free from triatomine bugs in Argentina.

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Aproximadamente 2 miliones de personas en Argentina se hallan infectadas con Trypanosoma cruzi, el agente etiológico de la enfermedad de Chagas, por lo cual constituye la principal enfermedad tropical del país. Al igual que en otros seis países del Cono Sur, Triatoma infestans es el único o principal vector de T. cruzi entre los seres humanos y los animales domésticos. En Argentina se estabeleció un Programa Nacional de Control de Chagas en 1962. Dicho programa perseguía la eliminación de las poblaciones domésticas y peridomésticas de T. infestans a través del rociado con insecticidas, y el control serológico de los donantes de sangre para prevenir infecciones relacionadas con las transfusiones. Este programa redujo fuertemente la prevalencia serológica de T. cruzi en todo el país. Por ejemplo, en jóvenes de 18 a 20 años de edad reclutados para el servicio militar, la seroprevalencia cayó del 10.0 por ciento en 1964 para aquellos nacidos en 1944 al 1.9 por ciento en 1993 para aquellos nacidos en 1975. Sin embargo, la estrategia vertical falló en alcanzar y sostener la fase de vigilancia en una extendida área rural con población dispersa debido a sus proprias limitaciones intrínsecas y al reducido o variable nivel de prioridad asignado a programas de salud rural. Se desarrolló y ensayó una estrategia de control alternativa del T. infestans en la Provincia de Santiago del Estero entre 1985-1989, y 1991-1992. Los resultados de esos proyectos demostraron que los rociados insecticidas llevados a cabo con la participación de la comunidad combinaron efectividad y compromiso de tal forma que produjeron un fuerte impacto sobre la reinfestación y la extensión del área bajo vigilancia entomológica. Esta experiencia ha sido transferida en una cascada de responsabilidades al personal del Programa Nacional de Control de Chagas, usando talleres participativos, guías de procedimientos, y entrenamiento práctico. Este personal transfirió la estrategia participativa usando métodos similares a los usados por agentes de atención primaria de salud y a voluntarios elegidos por sus proprias comunidades (líderes comunitarios)...

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